When a large area of a composite structure is monitored by a SHM system, a network of a large number of transducers may be used for that purpose. The transducers may be acoustic wave emitters (“actuators”) and/or detectors (“sensors”). These transducers may form combinations of actuator-sensor paths that are many times more numerous than the total number of transducers in the array. It is very common for a transducer network to produce hundreds to thousands of signals in each scan of the plurality of possible paths.
Because of the differences that may occur among the path lengths and the paths due to the surrounding geometry and the possible diversity of sensor installation, the signals of different paths typically vary in quality. Signals of some paths may be too weak to provide reliable information about a region of the structure through which the acoustic wave signal passes. The signal energy and the optimal frequencies along different paths are typically also very different.
To ensure the quality of the signals and the accuracy of the subsequent signal processing for damage detection, it is desirable to pre-process the network signals and optimize the operational excitation-detection conditions. However, in systems with a large number of such signals, it may be impractical to perform this pre-processing manually. An automatic pre-processing method is therefore needed.